Carburetor



Jan. 7, 1936.

c. H. KIRBY 2,026,788

CARBURETOR Filed Aug. 12, 1952 5 Shets-Sheet- 1.

Jan. 7, 1936.

c. H. KIRBY 2,026,788

CARBURETOR Filed Aug, 12, 1932 5 Sheets-Shet 2 5 Sheets-Sheet 5 c. H. KIRBY CARBURETOR Filed Aug. 12, 1932 Jan. 7, 1936.

1 fiarias' 2? 2616 CARBURETOR Filed Aug. 12, 1952 5 Sheefcs-Shee t 4 Patented Jan. 7, 1936 UNITED} PATENT OFFICE CARBURETOR tion of Illinois Application August 12, 1932, Serial No. 628,497 Claims. (Cl. 261-41) This invention relates to carburetors for internal combustion engines.

It is an object of this invention to provide an improved carburetor having superior operating characteristics in that the proportioning of fuel and air is automatically varied to produce the desired mixture of quantities for divergent operating conditions.

It is another object of this invention to provide an improved carburetor embodying a novel and advantageous mixture control for cold starting and warming up a cold engine. It has heretofore been advisable to use some form of ported or spring held unbalanced choke valve to prevent overchoking by a careless operator and it is accordingly an object of this invention to provide a starting control operating to provide an increased proportion of fuel, under the control.

of the operator, without flooding or overchoking after the engine has been started, this control being such that if left on too long the operator will be advised thereof by a speeding up of the engine while idling.

It is another object of this invention to provide an improved carburetor for automotive types of internal combustion engines, the carburetor having independently operating systems of fuel supply that can be separately calibrated to secure exact coordination over a wide range of engine requirements, thus providing very efficient fuel and air mixture ratios for the varying mixture requirements caused by speed and load variations of the engine. It is well known that automotive carburetion has the most diflicult and opposing mixture requirementsdue to the wide range of operating conditions and the demand for snappy acceleration under load from idling speeds as well as economy under normal operating conditions, and maximum possible power output at'high speeds and wide open throttle. These three major requirements are opposed to each other in many respects and no carburetor heretofore offered has given optimum results in each respect. For example, a racing carburetor fails to present good economy and operates poorly under traflic conditions while a good carburetor for city driving has not been the best for highspeed operation or economy. My improved carburetor meets these diverse requirements in a highly satisfactory manner due to the independent control of two separate but overlapping fuel supply systems which supple ment each other.

The carburetor of this invention embodies a h' number of improvements over that disclosed in my copending application Serial No. 607,053 filed April 23, 1932 entitled Carburetor. The present carburetor also differs therefrom in that a double Venturi structure is utilized, the outer part of the inner vent-uri being arranged as a re- 5 placeable sleeve, the profile of which can be varied to change the capacity limit of the carburetor.

Other and further important objects of this invention will become apparent from the following description and appended claims. 1 This invention (in a preferred form) is illustrated in the drawings and hereinafter more fully described.

On the drawings: Figure l is a plan or top view of an anterior 15 throttle type of down draft carburetor embodying the preferred form of this invention.

Figure 2 is a side elevation thereof partly broken away to show the primary fuel metering arrangement. 2

Figures 3 and 4 are views similar to Figure 2 showing different stages in the operation of the primary fuel metering valve.

Figure 5 is a broken section on the line V--V of Figure 1 showing the fuel supply to the secondary fuel metering valve and to the float chamber.

Figure 6 is a diagrammatic layout of the fuel passages of the carburetor.

Figure 7 is a fragmentary section showing the primary fuel delivery from the metering valve of Figures 2 to 4 to the inner venturi.

Figures 8 and 9 are similar sections of the air valve taken on the line VIII --VIII of Figure l to show the effect of the choke control thereon.

Figure 10 is a section of the air valve taken on the line X-X of Figure 9.

Figure 11 is a vertical section corresponding to Figure 5 of a modified form of my invention as applied to a carburetor of the more usual postew rior throttle type.

Figure 12 is a fragmentary sectional view showing a modified float bowl arrangement.

As shown on the drawings:

The anterior throttle type of down draft carburetor illustrated in Figures 1 to 10 comprises a body member 2|] containing a float chamber 2| and a mixing chamber or passage 22 terminating at its lower end in a mounting flange 23 and embodying a primary Venturi restriction 24 therein. A throttle valve 25 is mounted in the intake end of the passage above the point of fuel introduction so that the valve controls the air supply to the mixing chamber, and thus also functions as a choke valve for starting purposes.

The fuel supply to the float bowl is best shown in Figure 5 in connection with the secondary fuel metering system to be later described. Fuel from any convenient source enters a passaged boss 26 on a cover 27 applied to the float chamber and passes through an inlet valve seat 28 controlled by a valve 29 actuated by a float 30. Fueladmitted past the valve 29 does not enter the chamber 2| directly but flows along a passage 3! leading to a secondary fuel wall 32 and overflows therefrom through a passage 33 leading to the chamber 2|: Thus the secondary fuel well is maintained full as long as the float valve is off its seat and the level of the fuel therein is considerably above the level of the fuel delivery orifices opening into the mixing chamber 22 so that a gravity or pressure head is maintained on the secondary fuel supply system.

The primary fuel supply system is best shown in the diagrammatic view, since a combination of Figures 2 and 7 is required to disclose the full structure. Fuel flows from the float chamber 2| through a port 34 into a chamber 35 and through a tapered orifice 36 in the chamber to passages 31 and 38, the latter being shown in Figure 7. The fuel delivery to the mixing chamber is to the throat of a secondary venturi mounted with its outlet end at the throat of the primary venturi 24 formed in the mixing chamber walls. The secondary Venturi body 39 is secured in place by a cap screw 40 passaged and having calibrated apertures 4| for the delivery of the fuel from the passage 38 to a groove 42 around an inserted member 43 forming the throat of the Venturi passage, a number of holes 44 delivering fuel from the groove to the throat of the venturi.

' The secondary venturi is of peculiar construction in that the body member 39 has the throat member inserted therein to most conveniently form the groove 42 and has an outer sleeve 45 applied thereto; both to define an annular outlet passage 46 for the secondary fuel and air mixture and to form means for varying the capacity of the carburetor by varying the effective throat area of the primary venturi 24 by varying the wall thickness or profile of the exterior. of the sleeve 45 as indicated by the dotted lines on Figure 5. With this arrangement of interchangeable sleeves, the primary venturi can be formed, if desired, an integral part of the wall of the mixing chamber or passage, and capacity requirements met by a change in the sleeve profile.

The primary fuel supply is under the control of a metering pin 41 movable downwardly into the tapered orifice or valve seat 36. The pin is yieldingly held extended in a vertically movable piston 48 which is under the control of both the throttle and the warm-up control corresponding in external appearance and operation to the usual dash choke control. The upper end of the piston carries a member 49 to which a lever 50 is pivoted, the member 49 being adjustable relative to the piston by means of a differentially threaded sleeve 5| carrying a knurled head 52, rotation of this sleeve serving to either depress or retract the piston relative to the member 49 to adjust the metering pin in the orifice to secure a proper idling fuel supply when the parts are in the position of Figure 2. The lever 50 points about a fulcrum pin 53 carried by a lever 54 used for cold starting and warm-up purposes, the lever being provided with a curved slot 55 for the pin so arranged that a counter clockwise rotation of the choke lever swings the pivot pin 53 outwardly aoaegree in the slot to permit the piston and metering pin to be raised by the spring 50 as well as materially change the leverage of the member 49 relative to the lever 50 and the pivot pin as shown in Figure 3. The other or left-hand end of the lever 50 has a pin 56 therein which rides on the edge of a cam lever 51 carried by the throttle shaft. When the throttle is closed for idling the cam lever 5'! depresses the-lever 50 and moves the piston and metering pin to the idling position when the choke or warm up control is in the off or running position shown in Figure 2. If the warm up control lever is pulled over to the start position by the usual bowden wire control 58 as shown in Figure 3, the opening of the throttle allows a further rise of the piston until the lever 50 strikes the-hub of the cam lever 57.

The lever 54 of the warm up control is mounted on a sleeve 59 journaled in a boss 60 on the side of the carburetor body, the boss having a transverse aperture 6| leading to the mixing chamber 22 below the throttle. The sleeve is ported as indicated at 62, to register with the aperture 6| when the choke is pulled out, and under such circumstances extreme suction in the mixing chamber may unseat a spring pressed ball valve 63 in the sleeve thus admitting air to the sleeve and thence to the mixing chamber.

It may be desirable to provide an inlet for a small amount of air besides that passing the ball valve 63, and such an arrangement is shown in Figure 9 where a ported plug partly closes the outer end of the passage 6| and a second port 9| on the sleeve 59 registers with said port when the sleeve is rotated to the warm up position.

The foregoing description has necessarily treated the general warm up control as a disjointed series of individual elements. In order to correlate the starting and warming up operations, a description of the sequence of operations appears desirable at this point. For extreme cold starting, the throttle is allowed to remain in the closed or idling position and the control lever 54 is shifted counterclockwise. The first part of this movement causes the pin 53 to swing out to the end of the slot 55 in the lever 50, only slightly raising the metering pin for a higher speed idle. Further movement of the lever 54 results in a direct lift of the lever 50 until the piston is raised to the position of Fig. 3. At the same time the a intermediate position of the lever 54 has turned the sleeve 59 sufliciently to open the passage 6| and after the engine starts the higher suction, caused by the higher idling speed, serves to unseat the ball valve 63 and admit suflicient additional air to avoid undue richness as the engine speeds up. Following the initial cold start movement of the lever 54 is back towards its normal position, lowers the metering pin towards normal relation to the throttle when the latter is at the idling position, and also closes the passage 6|. To warm up the engine after starting, the control lever 54 is only returned part way, lowering the metering pin into the slightly enriched range and leaving the passage 5| open so that the ball valve can open in response to the high idling suction. In this position the metering pin is slightly lifted from the normal idling position and enough air is bypassed through the passage 6| to increase the quantity of idling mixture to offset the effects of a cold engine, causing an increase in the idling speed sufiicient to warn the operator that the control lever has not been returned to normal running position.

Above the idling speed the warm up control has an increasing effect since the pivot pin 53 is moved away from the center of the lever '50 and causes an increased lift of the metering pin in response to opening movement of the throttle. The secondary fuel supply system comprises an outlet valve seat 64 at the bottom of the well 32 as best shown in Fig. 5, the outlet therefrom leading through a passage 65 to the annular space at beneath the sleeve 55 on the secondary venturi. An air bleed passage into the passage 65 is indicated at 66 in Fig. 5, and is shown on the diagrammatic view of Figure 6 as having an adjustable atmospheric vent t'l for controlling the volume of air flow. It will be understood that since the passage 85 is subject to engine suction the delivery of fuel thereto from the valve seat 6% would be accelerated by such suction.

The adjustable air bleed afiords a means for controlling the varying fuel flow due to suction variations since an unrestricted air bleed would nullify the effect while the omission of the air bleed would give the full effect. It will thus be evident that the rate of fuel flow above that caused by the gravity head is under full control so that the primary and secondary fuel supplies can be correlated to produce an ideal fuel and air mixture over the entire operating range.

The flow of fuel past the valve seat 66 is controlled by a valve 68 the stem 69 of which carries a piston it reciprocable in a vacuum cylinder it connected to the mixing chamber 22 by apassage it which causes high suction in the carburetor to pull down the piston and shut ofi the flow of fuel. The valve 68 and piston l are normally urged upwardly by a spring 83 calibrated to open the valve under load conditions represented by an engine suction less than that existing under,

idling conditions. The valve W is provided primarily as a shut off valve for the secondary fuel supply when the engine is operating in the idlin and part load range, and the strength of the spring 13 can be predetermined in relationship to the cylinder size and manifold vacuum to cause the valve 68 to initially open at any desired point in the operating range since the vacuum is a maximum at idling and tapers off as the throttle is opened up and the engine load increases.

The cylinder H is formed on a member It screwed into the top of the well 32 and serves as a guide bushing for the stem 69. At each end of the guide portion the member it is recessed to cooperate with tapered seats 15 formed on the stem 69 so that at either extremity of the stem motion, leakage of fuel is prevented past the stem, into the cylinder H and thence through the suction passage to the mixing chamber 22. This refinement is desirable since manifold suction acts beneath the piston ill and would be suflicient to draw fuel up past the valve stem 68 thus upsetting the metering characteristics of the carburetor.

Under certain operating conditions it may happen that the float valve closes the fuel inlet valve 29 while the valve 68 is open for the delivery of fuel, so that the well 32 might run dry when the engine required the fuel normally delivered thereby. To provide against this possibility I have disclosed means in Figures and 12 to withdraw fuel from the float bowl when the fuel level therein is high enough to shut off the inflow of fuel past the valve 29. In Fig. 5 a valve 90 is carried by the float 30 which valve opens a passage 9| from the float bowl 2| to a restricted orifice 92 and thence through tubing 93 to the intake side of the usual fuel pump which delivers fuel to the carburetor inlet 26. In this form of the device the valve 90 closes the passage Sl'when the float is down and opens it when the float rises so that under such circumstances the fuel pump will withdraw fuel from the float bowl until the fuel level falls far enough to open the valve 29 thus assuring the maintenance of a supply of fuel to the well 32.

The alternative form of Fig. 12 dispenses with the float actuated valve 80 and substitutes an open tube at the top of which terminates slightly below the high liquid level 95 corresponding to the closed position of the valve 29. Thus when the float 3t closes the valve 29 the tube M will draw fuel from the bowl-until the top of the tube is uncovered the resulting lowering of the fuel level serving to open the valve 29.

An accelerating pump is shown in the diagrammatic View as being operated by a link it connected to a throttle lever if, the pump comprising a ported piston it on a piston rod it connected to the link it. A follow-up piston 8d, slideable on the piston rod til is caused to yieldingly follow the piston '38 on its pumping stroke by a spring 80, the ports in the piston allowing the passage of a portion of the fuel which acts to retard the movement of the follow up piston during the actual pumping stroke, the fuel so bypassed being delivered as a delayed charge serving to.

prolong the acceleration interval until the carburetor reaches equilibrium for the increased load represented by an increased throttle opening. The pump draws fuel from the float chamber 22 through a passage 82 and check valve 83 and delivers through a passage M to the mixing chamber on the anterior side of the venturis therein, an air vent 85 being provided to prevent a syphon effect due to the suction in the mixing chamber.

The modified form of carburetor shown in Fig. 11 illustrates the application of my improved fuel control systems to a down draft carburetor incorporating the more usual form of throttle valve 85 located between the venturis and the engine manifold, a primary venturi 81 being inserted in the mixture passage with its throat adjacent the outlet end of the secondary venturi. In this form of carburetor a usual type of choke valve 83 may be used at the air inlet end of the mixture passage in place of the previously described warm up con trol, and a vacuum connection 89 for controlling the secondary fuel valve 68 is lcd to a point on the engine side of the throttle valve in order that the control may be responsive to engine suction.

In the operation of the preferr d form of anterior throttle carburetor, the primary fuel supply system is subjected to engine or manifold suction plus the additional suction .created by the inner or secondary venturi so that it is necessary to meter or limit the flow of fuel which would otherwise be a maximum at idling. The primary fuel delivery is further conrolled by the adjustable leverage provided by the combination of the throttle cam and the warm up control which acts to enrichen the mixture over the entire operating range. Since the primary and secondary fuel supplies are independently controllable, the. calibration of each can be adjusted to obtain an exact coordinationaffording the most desirable mixture ratios for each distinctive phase of engine operation such as prompt starting and rapid warming up without danger of flooding, economical operation at part loads, and maximum power output with the least possible increase in fuel supply. The control of the secondary fuel supply rests in the calibration of the spring and in the air bleed which eliminates an adjustable proportion of the suction efiect on the fuel delivery, the secondary fuel supply coming into action as the primary fuel supply leans off due to decrease in the engine suction.

I am aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this invention, and I, therefore; do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim as follows:

1. A carburetor of the double Venturi type including an inner venturi concentrically located to discharge into the throat of an outer venturi, said inner venturi having an annular fuel and air mixture discharge space formed by an applied sleeve the profile of which determines the effective capacity of the carburetor, means for supplying fuel under-a gravity head to said discharge space and vacuum operated means for cutting off the supply of fuel at high suctions within the carburetor.

2. A double Venturi carburetor including an inner venturi having a plurality of separate fuel discharging outlets therein, means for supplying fuel to one of the discharge outlets in response to suction acting thereon, means for controlling the fuel supply through one of said discharge outlets over the operating range, and means for supplying fuel under a gravity head to another of the discharge outlets.

3. A double Venturi carburetor including an inner venturi having a plurality of separate fuel discharging outlets therein, means for supplying fuel to one of the discharge outlets in response to -10 suction acting thereon, means for supplying fuel under a gravity head to another of the discharge outlets, and means for independently controlling each of the fuel supplies to coordinate the same to produce a balanced fuel and air mixture in the carburetor over the operating range thereof.

4. A double Venturi carburetor including an inner venturi having a plurality of separate fuel discharging outlets therein, means for supplying fuel to one of the discharge outlets in response to suction acting thereon, means for controlling the fuel supply through one of said discharge outlets over the operating range, means for supplying fuel under a gravity head to another of the discharge outlets. and suction actuated means adapted to cut off said second fuel supply at a predetermined high suction whereby the said fuel supply supplements the first mentioned fuel supply at operating conditions above small loads.

5. A double Venturi carburetor including an inner venturi having a plurality of separate fuel discharging outlets therein, means for supplying fuel to one-of the discharge outlets in response to suction acting thereon, means for controlling the fuel supply through one of said discharge outlets over the operating range, means for supplying fuel under a gravity head to another of the discharge outlets, and an adjustable air bleed into said second fuel supply to control the added effect of suction thereon.

6. In a carburetor including a mixture passage and a throttle valve, means for supplying fuel to said mixture passage including a valve seat in the supply duct, a metering pin cooperating with said valve seat to vary the fuel flow there past, and independently movable means aoea'ree for cumulatively adjusting said metering pin, comprising a cam associated with the throttle valve, a lever engaging the cam at one end and pivotally and adjustably connected to said metering pin near the middle of the lever, a warmup control comprising a movable fulcrum pin engaging the other end of said lever and movable to both vary the leverage of said lever and to shift the metering pin relative to the valve seat, and a distance type of choke control for operating said movable fulcrum pin.

7. In a carburetor including a mixture passage and a throttle valve, means for supplying fuel to said mixture passage including a valve seat in the supply duct, a metering pin cooperating with said valve seat to vary the fuel flow there past, and means for operating said metering pin, comprising a cam associated with the throttle valve, a lever engaging the cam at one end and pivotally connected to said metering pin near the middle of the lever, a warm-up control comprising a movable fulcrum pin engaging the other end of said lever and movable to both vary the leverage of said lever and to shift the metering pin relative to the valve seat, operating means for said movable fulcrum pin,and means associated with said operating means to admit supplemental air to the carburetor when the fulcrum pin is shifted to the starting and warm-up position. 7

8. In a carburetor including a mixture passage and a throttle valve, means for supplying fuel to said mixture passage including a valve seat in the supply duct, a metering pin cooperating with said valve seat to vary thefuel flow there past, and means for operating said metering pin, comprising a cam associated with the throttle valve, a lever engaging the cam at one end and pivotally connected to said metering pin near the middle of the lever, a warm-up control comprising a movable fulcrum pin engaging the other end of said lever and movable to both vary the leverage of said lever and to shift the metering pin relative to the valve seat, and suction responsive means associated with the movable fulcrum pin to admit supplemental air to the carburetor when said fulcrum pin is set to increase the leverage of said lever.

9. A carburetor of the class described comprising a body member having a suitable air passage therethrough,including a venturi and throttle valve in said passage, a primary and a secondary fuel metering system having separate metering and delivery oriflces, a well supplying fuel under a gravity head to said secondary fuel metering system, a float chamber supplying fuel to the primary fuel metering system in response to suction thereon, means for supplying excess fuel to said well and for conducting the excess fuel from said well to the float chamber, a float actuated valve controlling the admission of fuel to the well, and means adapted to temporarily withdraw fuel from said float chamber when the float shuts off the admission of fuel.

10. A carburetor of the class described comprising a body member having a suitable air passage therethrough, including a venturi and throttle valve in said passage, a primary and a secondary fuel metering system having separate metering and delivery orifices, a well supplying fuel under a gravity head to said secondary fuel metering system, means adapted to shut off the secondary fuel metering system under idling conditions, a float chamber supplying fuel to the primary fuel metering system in response to suction thereon, means for supplying excess fuel to said well and for conducting the excess fuel from said well to the float chamber, a float actuated valve controlling the admission of fuel to the well, and means adapted to temporarily withdraw fuel from said float chamber when the float shuts off the admission of fuel. 11. A carburetor comprising a well, a fuel supply therefor, a constant level fuel reservoir at a lower level relativelto the well, an overflow passage from said well to ,the reservoir, a fuel outlet connected to the well and located below the fuel level therein whereby a positive static fuel head is maintained on the fuel delivered. from said fuel outlet, means for air bleeding the fuel supply to said fuel outlet to reduce the effect of suction thereon, and means adapted to temporarily withdraw fuel from said float chamber when the float shuts off the admission of fuel.

12. A carburetor comprising a well, a fuel supply therefor, a constant level fuel reservoir at a lower level relative to the well, an overflow passage from said well to the reservoir, a fuel outlet connected to the well and located below the fuel level therein whereby a positive static fuel head is maintained on the fuel delivered from said fuel outlet, means for air bleeding the fuel supply to said fuel outlet to reduce the effect of suction thereon, means for cutting off the flow of fuel to said fuel outlet under idling conditions, and means adapted to temporarily withdraw fuel from said float chamber when the float shuts off the admission of fuel.

13. A carburetor comprising a well, afuel supply therefor, a constant level fuel reservoir at a lower level relative to the well, an overflow passage from said well to the reservoir, a fuel outlet connected to the well and located below the fuel level therein whereby a positive static fuel head is maintained on the fuel delivered from said fuel outlet, means for air bleeding the fuel supply .to' said fuel outlet to reduce the eflect of suction thereon, suction responsive means adapted to cut off the flow of fuel to said fuel outlet at high engine suctions. and means adapted to temporarily withdraw fuel from said float chamber when the float shuts off the admission of fuel.

14. In a carburetor including a mixture passage and a throttle valve, means for supplying fuel to said mixture passage including a supply duct having a valve seat therein, a metering pin 10 cooperating with said valve seat to vary the fuel flow past the seat, a lever pivotally and adjustably connected to said metering pin, and sep-, arate means for cumulatively operating said metering pin, one of said means comprising a 15 cam associated with the throttle valve and engaging one end of said lever, and the other of said means comprising a warm-up control having a movable fulcrum pin engaging the other end of said lever and movable to both vary the go leverage of said lever and to shift the metering pin relative to the valve seat.

15. In a carburetor including a mixture passage and a throttle valve, means for supplying fuel to said mixture passage including a duct 25 having a valve seat therein, a metering pin cooperating with said valve seat to vary the flow of fuel to said passage, a lever pivotally connected to said metering pin, a. first means for operating said metering pin including a first operating element associated with the throttle valve and engaging one end of said lever, and a second means for operating said metering pin comprising a warm-up control having an operating element engaging the other end of said lever, said first operating element serving as a fulcrum for the lever when the lever is actuated by the second operating element, and said second operating element serving as a fulcrum for the lever when the lever is actuated by the first 0perating element.

- CHARLES H. KIRBY. 

